I have contacted ACube regarding the SAM440ep, and can confirm that it will not start up with a RadeonHD card connected, while the SAM440 flex can. Each motherboard has its own variation of UBoot, and the SAM440ep's version is currently unable to start properly with a Radeon HD 2400 plugged in, despite having no trouble with older cards (e.g., a Radeon 9000). Hopefully this will be rectified at some point. In the mean-time SAM440ep users will be unable to use Radeon HD 2400 cards. So far this has only been tested with Radeon HD 2400 cards, and not Radeon X1300 or X1550 cards.